There are known side airbag apparatuses for deploying between a seat occupied by a vehicle occupant and a door for entering and exiting the vehicle by the occupant. Such side airbag apparatuses cushion a side-collision (side-impact collision) load and protect the vehicle occupant when a side-collision occurs to the vehicle.
A side airbag provided to a seatback for supporting the back of the vehicle occupant in the seat is known as such a side airbag apparatus, as disclosed in Japanese Patent Application Laid-Open Publication No. 2003-137059 (JP 2003-137059 A), for example.
In the side airbag apparatus disclosed in JP 2003-137059 A, the outer circumferences of two flat pieces of foundation cloth are sewn together to form an airbag. The airbag is constructed of a non-expanding section that is not inflated with a fluid gas, and a plurality of inflating chambers that is inflated with the fluid gas. An elastic structure is used for the non-expanding section to allow the non-expanding section to stretch when the airbag is deployed. Specifically, an elastic structure is used for the non-expanding section to stabilize the airbag when the airbag is deployed and inflated. The elastic structure of the non-expanding section of the airbag is formed with slits.
However, in the side airbag apparatus disclosed in JP 2003-137059 A, because the elastic structure of the non-expanding section of the airbag is formed with slits, the slits interfere with the armrests and other components present in the vehicle compartment, and the airbag sometimes cannot be immediately deployed.
Moreover, because the non-expanding section not inflated by fluid gas is an elastic structure in the side airbag apparatus, the shape of the upper and lower channels is hard to stabilize, and deviation of the protected area from the intended range is possible.